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Sunday, November 23, 2014         

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Scope mapping island skies

Pan-STARRS 1 has begun a broad survey to build a census of astronomical objects

By Helen Altonn

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One of the most powerful telescopes in the world is surveying the sky from Haleakala, Maui, searching for near-Earth killer asteroids and mapping billions of other objects to help understand the nature of the universe.

Since becoming operational for scientific uses May 13, Pan-STARRS 1 has mapped one-sixth of the sky visible from Hawaii, which is "unprecedented," said PS1 Director Kenneth Chambers at the University of Hawaii Institute for Astronomy.

The 60-inch-diameter telescope will continue mapping that much of the sky every month, detecting stars 10 million times fainter than those visible to the naked eye, as well as black holes, brown dwarfs, galaxies, quasars, dark matter and other astronomical phenomena.

"There are going to be a lot of discoveries, I'm sure, just having so much more coverage of the sky," said Nicholas Kaiser, an institute astronomer and principal investigator of the Pan-STARRS project. "A lot of things are happening all the time, but we just miss them because no one is looking."

Until now, that is. Chambers and Kaiser said in separate interviews that the remotely operated telescope -- the prototype for an array of four telescopes planned in a Pan-STARRS system -- is an enormous tool for astronomy.

"Asteroids are cool stuff, but there is a lot of other cool stuff now that we're on the sky," Chambers said. "The supernova people are going crazy. There are dozens and dozens of supernovae. They're finding them every night."

Astronomers and engineers at the Institute for Astronomy designed and built the project at Haleakala's summit, and the institute's Advanced Technology Research Center at Pukulani is operating it by computer.

A second Pan-STARRS telescope will be built on Haleakala, and the UH 88-inch telescope site on Mauna Kea has been selected for the full array.

UH-Manoa formed a consortium of 10 academic institutions in the U.S., United Kingdom, Germany and Taiwan that are contributing more than $11 million for the first Pan-STARRS operation in return for proprietary access to the data for 3 1/2 years, Chambers said. The data then will be released for worldwide scientific use, he said.

Kaiser said the consortium has about 200 astronomers interested in getting data for scientific analysis. His interest is cosmology, "looking at the behavior of the universe on larger scales," he said. "My object is to map out the dark matter in the universe. Once you know that, it tells you about dark energy driving the expansion of the universe."

It will take a couple of years to accumulate the necessary data, he said, "so we're going to have a lot of fun in the meantime."

Institute astronomer John Tonry invented the world's largest digital camera for Pan-STARRS 1. It has 1,400 megapixels and can photograph an area of the sky as large as 36 full moons in a single exposure. It is designed to scan the skies automatically for objects that move or change brightness from night to night.

The camera takes more than 500 exposures each night and sends about four terabytes of data -- equivalent to what 1,000 DVDs can hold -- to the Maui High Performance Computing Center in Kihei for processing.

The center's "workhorse" system calibrates and registers the data and analyzes every object to "categorize it as something we know or don't know," Chambers said. An institute team at Manoa logs into the computers at Kihei and does image processing, he said. Another bank of computers takes the catalogs and puts them into an enormous database for "Google-like queries" by scientists seeking particular information.

Pan-STARRS 1 generally is regarded as an optical telescope, but three of five filter bands used are beyond the range of the human eye, Chambers said.. "The science consortium is funding it for 12 key projects, from near asteroids in our back yard to things at the edge of the universe."

Pan-STARRS basically is taking a census of "everything surrounding us in the universe," he said, pointing out the data can be used for a wealth of science, which makes the project "much, much more powerful."

But it is an enormous technical challenge to access data on 30 billion objects, he said. "You can't do it by thumbing through a catalog like a phone book. You can only do it in the database. It requires sophisticated computer technology."

It represents "a new kind of statistical science," Chambers said. "We're trying to systematically survey the sky in a clever way but leave it to astronomers to dig into and find all the things we couldn't imagine being there, and they'll find them in ways they couldn't before because they didn't have a large number of objects."






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